Among other studies on ZIF-8 densification, there is a study by Bazer-Bachi et al. 39 (who also densified SIM-1). The authors applied a wide range of pressures and showed that the crystallinity of ZIF-8 was preserved upon compression up to ∼230 MPa. At the same time, the loss in BET surface area was about 11%, with the ZIF-8 pellet reaching 1278 m 2 g −1, while the pristine ZIF-8 powder exhibited 1433 m 2 g −1. Noteworthily, these results are in good agreement with the ones reported by Ribeiro et al. 37 and Chapman et al. 38 Upon compression, SIM-1 demonstrated a similar trend with a 28% drop in surface area (516 vs. 370 m 2 g −1) at a decent pressure of ∼400 MPa while preserving its framework topology according to its XRD pattern.

Moreira et al. 52 demonstrated the reverse selectivity of UiO-66 towards liquid-phase separation of xylene isomers. Indeed, the obtained results suggested o-xylene selectivities of 1.8 and 2.4 with respect to m- and p-xylene, at 40 °C with n-heptane as the eluent. Besides, the authors showed that the selectivities were retained upon compression, meaning that no major modification of the pore network took place upon compression. Interestingly, the authors stated that at low concentrations the selectivity values of UiO-66 were comparable to the ones previously reported for MIL-53. However, the latter failed to separate m- and p-isomers unlike UiO-66. Interestingly, they also prepared MIL-100 pellets following the pelletization method and compared the thus formed bodies with the granules in terms of NH 3 adsorption. The latter exhibited higher adsorption capacity at 25 °C (4.4 vs. 3.6 mmol g −1), suggesting that upon pelletization, the parent powder underwent more drastic structural and textural changes as compared to granulation. This was supported by XRD and N 2 physisorption measurements. R. Bingre, B. Louis and P. Nguyen, An Overview on Zeolite Shaping Technology and Solutions to Overcome Diffusion Limitations, Catalysts, 2018, 8, 163, DOI: 10.3390/catal8040163. Less than 10,000 people have ever won the right to call themselves one of the Best Craftsmen in France. MOF winners retain their title for life. Many choose to join the National Society of Meilleur Ouvrier de France, a sort of alumni society for winners. The title is taken so seriously that sporting such a collar fraudulently is a crime punishable by prison-time.

R. V. Jasra, B. Tyagi, Y. M. Badheka, V. N. Choudary and T. S. G. Bhat, Effect of Clay Binder on Sorption and Catalytic Properties of Zeolite Pellets, Ind. Eng. Chem. Res., 2003, 42, 3263–3272, DOI: 10.1021/ie010953l.

X. Fang, B. Zong and S. Mao, Metal–Organic Framework-Based Sensors for Environmental Contaminant Sensing, Nano-Micro Lett., 2018, 10, 64, DOI: 10.1007/s40820-018-0218-0. Fig. 1 Schematic representation of the pelletization process applied to polycrystalline MOF powder. An aqueous spray-drying synthesis of the Zn-imidazole ZIF-8 was done by Tanaka et al. 134 In a typical synthesis, an aqueous suspension containing Zn-acetate and 2-methylimidazole was spray-dried at T in = 150 °C and a feed rate of 5 mL min −1. These conditions yielded dense spherical particles with an average size of 3.9 μm as confirmed by SEM and TEM. However, the XRD results suggested the formation of an unknown phase different from that of the original ZIF-8. Moreover, the product poorly adsorbed nitrogen as revealed by N 2 sorption measurements. Notably, the authors observed the coordination of dissolved species and therefore the solution turning into a suspension right before spraying. The authors explained this phenomenon as due to the hindrance of crystallization created by acetic acid, a by-product originating from the Zn-precursor. The presence of the acid in the as-synthesized product was demonstrated by means of FTIR spectroscopy and TGA. Accordingly, during the spray-drying process, the as-released acetic acid caused a rearrangement of Zn-(2-methylimidazole) bonds, leading to the amorphization of the final product due to the incomplete coordination of the ligands around the metal. Interestingly, the presence of non-coordinated ligands was similarly evidenced by TGA. However, redispersing the spray-dried particles in an alcohol enabled the recrystallization and thus the formation of the targeted ZIF-8 framework. Interestingly, the size of the alcohol molecule influenced the size of the nanocrystals: specifically, the longer the carbon chain the larger the nanocrystals. However, the microbead size remained in the same range. Upon recrystallization, the product yielded an XRD pattern characteristic of ZIF-8 with a S BET of 1440 m 2 g −1, which is consistent with the results published elsewhere. 135 Surprisingly, once these ZIF-8 microbeads were redispersed in an alcoholic solution, they undergo a transition from dense to hollow superstructures. Hence, the recrystallization process is fed by gradually dissolving the amorphous by-product from the surface to the core of the microbeads. The MOF title is really unique. It carries an important historical legacy and recognizes work approaching perfection. It is a true honor to receive recognition for one'speers and country. Today, I proudly represent and further with my best abilities the values of professional excellence, innovation and transmission.” explains Meilleur Ouvrier de France ChefChristian Segui What is the competition about?

Finally, other less-popular techniques have been successfully applied for shaping MOFs, among which have been reviewed the so-called molecular gastronomy, ice-templating (also called freeze-casting), and phase separation (also called spinodal decomposition). These three techniques presented very low impact on the physicochemical properties of the MOFs applied and are therefore worth investigating more in detail. It should be noted, however, that ice-templating and phase separation both involve the creation of a second level of porosity macrosized (>50 nm) following the replication of ice crystals and polymers, respectively. Technically, any French citizen 23 years or older who pays the 60-euro entrance fee can compete, but few have the preparation and dedication necessary to make a serious bid for the title. A particularity of the competition is the absence of podium. Indeed, the MOF title is awarded based on the average marks obtained in the tests, so there may well be several winners or none, if no one has reached the required score to become a laureate. V. Finsy, L. Ma, L. Alaerts, D. E. De Vos, G. V. Baron and J. F. M. Denayer, Separation of CO 2 / CH 4 mixtures with the MIL-53 (Al) metal–organic framework, Microporous Mesoporous Mater., 2009, 120, 221–227, DOI: 10.1016/j.micromeso.2008.11.007.

The paste formulation is crucial and requires special attention. Indeed, mixing of the parent powder with a liquid should yield a paste with suitable rheological properties to enable extrusion. There are many aspects which define the flow behavior such as the size and shape of the powder particles, their chemical properties, etc. Overall, the paste viscosity is dictated by the liquid content and can be decreased upon increasing the total liquid/solid ratio. More viscous pastes might require higher pressures for displacement within an extruder; however, unlike pelletization, extrusion does not affect as much the compaction of the particles as they are suspended in a liquid. Besides, in some cases the flowability, plasticity, or ability of the paste to withstand deformation upon extrusion can be enhanced by adding plasticizers. These are typical organic compounds based on cellulose or polyalcohols which facilitate the formation of the overall network. Generally, they are removed from the final extrudate composition by calcination. R. R. Salunkhe, Y. V. Kaneti and Y. Yamauchi, Metal−Organic Framework-Derived Nanoporous Metal Oxides toward Supercapacitor Applications: Progress and Prospects, ACS Nano, 2017, 11, 5293–5308, DOI: 10.1021/acsnano.7b02796. The craftsmanship exhibition has been held every three to four years and showcases different professions including florists, carpenters, butchers, jewelry makers, and of course pastry chefs, to name just a few. Along with the title, winners receive a medal and state diploma.

The MOF competition and its preparation are definitely in my top lifetime memories. The hours of preparation, the stress of the competition, the recognition for all the work and commitment, have alla All has changed me forever. I have pushed myself beyond what I imagined possible and it certainly contributed in making me a better professional.” continues Meilleur Ouvrier de France Chef Thomas Marie The culinary connection Y. Zhao, Z. Song, X. Li, Q. Sun, N. Cheng, S. Lawes and X. Sun, Metal organic frameworks for energy storage and conversion, Energy Storage Mater., 2016, 2, 35–62, DOI: 10.1016/j.ensm.2015.11.005. and their applications as anodes in lithium and sodium ion batteries, Coord. Chem. Rev., 2019, 388, 172–201, DOI: 10.1016/j.ccr.2019.02.029. Recently, 3D printing has been applied to a large number of structured adsorbents and catalysts. Thus, Al 2O 3 was shown to be printable into monoliths exhibiting high catalytic efficiency as well as good recyclability. 95 Zeolites 13X and 5A have also been printed into monoliths for CO 2 removal purposes, 96 while a 3D-printed zeolite (ZSM-5) has been probed for CO 2, CH 4 and N 2 separation. Among the other printed structures can be found carbons, 97 amorphous aluminosilicates 98 and other classes of adsorbents. 99

In particular, they performed a full study on the production of UiO-66 spherical microbeads. First of all, they found that introducing a continuous flow reactor before the spray-dryer is a crucial step as the application of the spray-dryer alone yielded an amorphous product, as reported by Mitsuka et al. 137 Moreover, the sole use of a continuous flow reactor without the spray-dryer gave rise to the product with a low yield (12%) as well as poor textural properties ( S BET = 708 m 2 g −1). Thus, the combination of both was required. The authors further showed that the optimal conditions for the synthesis of UiO-66 and its derivatives included an inlet temperature of 180 °C, a flow rate of 336 mL min −1 and a feed rate of 2.4 mL min −1. The chosen inlet temperature corresponds to the minimum temperature required for the complete evaporation of the solvent, DMF. The UiO-66 microbeads produced under these conditions yielded dense spherical superstructures with an average size of 4.3 ± 2.6 μm composed of individual nanoparticle aggregates ( Fig. 16d). XRD confirmed the presence of the UiO-66 structure. In terms of textural properties, the spray-dried microbeads exhibited pronounced porosity with a high S BET of 1106 m 2 g −1, which is in good agreement with that of UiO-66 produced by classical solvothermal methods (1150–1250 m 2 g −1). 139,140 Fig. 4 Typical wet granulation equipment: a high shear-rate mixer (Maschinenfabrik Gustav Eirich GmbH & Co KG), also referred to as a granulating pan (a) with an adjustable speed and direction of rotation; and a disc pelletizer (ERWEKA GmbH) also referred to as a rolling machine (b) with a controllable speed and inclination angle. Schematic representation of the wet granulation process: (c) mixing; (d) wetting and nucleation; (e) growth; and (f) spherization by attrition and breakage.Granulation is the last industrially-mature technology reviewed herein, and allows producing millimeter-sized grains. Two types of granulation techniques are typically discussed: wet granulation, when powders are aggregated in a high-shear rate mixer in the presence of a solvent; and dry granulation, when grains are obtained from a previously shaped object either mildly crushed and sieved, or spheronized. Due to higher stresses applied, the dry granulation implies more severe losses in the initial physicochemical properties of the MOFs, while the wet granulation has a less pronounced effect and therefore might be more adequate. Especially, replacing water with another solvent with a lower surface tension is highly beneficial. This change of mind return policy is in addition to, and does not affect your rights under the Australian Consumer Law including any rights you may have in respect of faulty items. To return faulty items see our Returning Faulty Items policy. Two step, continuous flow spray-drying method, dense structures Garzon-Tovar et al. 138 also reported the spray-drying of a series of MOFs with high-nuclearity. To do so, they combined continuous flow and spray-drying methods ( Fig. 16b and c). As in the case of Mitsuka et al., 137 the former is beneficial to initiate the nucleation step, while the latter favors the crystal growth. Thus, the so-called spray-drying continuous flow-assisted synthesis was applied to produce spherical microbeads of UiO-66 and its derivatives.